Field of the Invention
The present invention relates to a semiconductor substrate, an image pickup element, and an image pickup apparatus.
Description of the Related Art
Conventionally, when an image pickup element such as, for example, a back-illuminated image sensor or a stacked image sensor is manufactured, photolithography is performed in steps of forming an on-chip color filter, an on-chip microlens, and a light-shielding film. A photomask or a reticle in which a wiring pattern is drawn is used during photolithography exposure. In this case, an alignment mark formed of a metal wire is used to realize alignment between a wafer and the mask. This alignment mark is formed in a scribe line or a chip region.
When the position of an alignment mark is detected by a semiconductor manufacturing apparatus during exposure, as disclosed in Japanese Unexamined Patent Application, First Publication No. 2011-9259, for example, a detection beam is emitted to the alignment mark and the reflection intensity thereof is measured. Thus, when a metal wire, a device, a bonding electrode, and the like, for example, are formed on an underlayer of the alignment mark, the reflection beams thereof are also detected.
As a result, when it is difficult to obtain sufficient contrast between the reflection intensity of the alignment mark and the reflection intensity of the metal wire, the device, the bonding electrode, and the like on the underlayer, the semiconductor manufacturing apparatus causes an error in recognition of the alignment mark and alignment accuracy of a wafer with the photomask or the reticle deteriorates. Moreover, the position of the metal wire or the device on the underlayer may be erroneously recognized as the position of the alignment mark, and a problem in which alignment is not realized may occur.
In order to prevent such a problem, conventionally, the metal wire, the device, and the bonding electrode are not formed on the underlayer of the alignment mark.